Variable displacement lubricant pump

ABSTRACT

A variable displacement lubricant pump for providing a pressurized lubricant for an internal combustion engine. The variable displacement lubricant pump includes a shiftable control ring, a pump rotor comprising a plurality of slidable vanes which rotate in the control ring, a hydraulic pressure control comprising a control chamber which comprises a lateral control chamber wall, and a control ring plunger shiftable along the lateral control chamber wall, a first eccentricity limiting opening arranged in the lateral control chamber wall, a second eccentricity limiting opening arranged in the lateral control chamber wall, and an eccentricity limiting control system which connects or disconnects the first eccentricity limiting opening and the second eccentricity limiting opening to atmospheric pressure dependent on a lubricant temperature. The hydraulic pressure control directly actuates and controls an eccentricity of the control ring.

CROSS REFERENCE TO PRIOR APPLICATIONS

This application is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/EP2013/071941, filed on Oct. 21, 2013. The International Application was published in English on Apr. 30, 2015 as WO 2015/058783 A1 under PCT Article 21(2).

FIELD

The present invention relates to a mechanical variable displacement lubricant pump for providing pressurized lubricant for an internal combustion engine.

BACKGROUND

The mechanical pump is directly driven by the engine and comprises a pump rotor with radially slidable vanes rotating within a radially shiftable control ring, whereby the control ring is pushed by a plunger pushing the control ring to a high eccentricity direction and thereby to a high pumping volume direction. The plunger is shiftably arranged within a control chamber. The pump comprises a pressure control system for controlling the discharge pressure of the pressurized lubricant leaving the pump. The pump's discharge pressure is controlled by controlling the position of the shiftable control ring, which is controlled by the pressure in the hydraulic control chamber. The eccentricity of the control ring is decreased or increased by moving the control ring plunger so that the discharge pressure can be controlled.

WO 2005/068838 A1 describes a variable displacement lubricant pump with an opening in the lateral control chamber wall. The opening is connected to atmospheric pressure, whereby an electric valve is provided to open or close the connection of the lateral wall opening to atmospheric pressure. The valve is controlled by an electronic temperature sensor so that the eccentricity of the control ring can be limited to a maximum eccentricity if the lubricant temperature is below or above a temperature limit.

WO 2010/146087 A2 describes a mechanical variable displacement pump with an opening in the lateral control chamber wall. The opening is provided in a slider which is shiftable in a radial direction so that the radial position of the opening can be varied within a particular range to vary the maximum eccentricity of the control ring. The radial position of the opening is controlled by a temperature sensitive mechanical actuator.

SUMMARY

An aspect of the present invention is to provide a variable displacement lubricant pump where the control ring has a variable maximum eccentricity and which has a simple construction.

In an embodiment, the present invention provides a variable displacement lubricant pump for providing a pressurized lubricant for an internal combustion engine. The variable displacement lubricant pump includes a control ring configured to be shiftable, a pump rotor comprising a plurality of slidable vanes which are configured to rotate in the control ring, a hydraulic pressure control comprising a control chamber which comprises a lateral control chamber wall, and a control ring plunger configured to be shiftable along the lateral control chamber wall, a first eccentricity limiting opening arranged in the lateral control chamber wall, a second eccentricity limiting opening arranged in the lateral control chamber wall, and an eccentricity limiting control system configured to connect or disconnect the first eccentricity limiting opening and the second eccentricity limiting opening to atmospheric pressure dependent on a lubricant temperature. The hydraulic pressure control is configured to directly actuate and to control an eccentricity of the control ring.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in greater detail below on the basis of embodiments and of the drawings in which:

FIG. 1 shows a schematic representation of a variable displacement lubricant pump including an eccentricity limiting control system, the pump being arranged in a lubricant circuit including an internal combustion engine;

FIG. 2 shows an embodiment of an eccentricity limiting control system;

FIG. 3 shows an embodiment of an eccentricity limiting control system; and

FIG. 4 shows an embodiment of an alternative arrangement of three overlapping eccentricity limiting openings.

DETAILED DESCRIPTION

In an embodiment of the present invention, the variable displacement lubricant pump is provided with a first and a second eccentricity limiting opening in the lateral control chamber wall. The eccentricity limiting openings can be (referring to the radial direction, i.e., the direction of the plunger movement path) arranged to overlap or can be arranged with a radial distance to each other so that the eccentricity limiting openings do not overlap in a lateral projection. An eccentricity limiting control system is also provided to connect or to disconnect the eccentricity limiting openings to atmospheric pressure dependent on a lubricant temperature T. The eccentricity limiting control system is provided with a valve arrangement downstream of the eccentricity limiting openings and allows the selective control of the connection of the eccentricity limiting openings to atmospheric pressure. This simple arrangement allows two different maximum eccentricities of the control ring to be chosen to adapt the maximum pump rate to the lubricant temperature T.

In an embodiment of the present invention, a third eccentricity limiting opening can, for example, be provided in the side wall of the control chamber to allow a finer adaptation of the maximum eccentricity and the maximum pump rate to the lubricant temperature T. Providing two or more eccentricity limiting openings which are individually switchable allows an individual programming of the maximum eccentricity limit which is not necessarily linear with the lubricant temperature T.

In an embodiment of the present invention, the eccentricity limiting control system can, for example, be provided with at least one bimetal element which causes the opening or the closing of the eccentricity limiting openings. A bimetal element is a simple, reliable and cost effective temperature-sensitive actuator. The bimetal element does not necessarily cause a direct closing of the eccentricity limiting openings, but can be provided downstream of the eccentricity limiting openings to block or unblock any flow through the respective eccentricity limiting opening.

In an embodiment of the present invention, every eccentricity limiting opening can, for example, be provided with a separate bimetal element which can directly close the respective conduit between the eccentricity limiting opening and the atmospheric pressure in the closed position of the bimetal element. The bimetal element serves as a valve body which directly closes a valve channel. The respective bimetal valve elements have different switching temperatures TS so that the maximum eccentricity can be adapted dependent on the lubricant temperature T in relation to the different switching temperatures. This arrangement provides a non-linear programming of the maximum eccentricity dependent on the lubricant temperature T.

In an embodiment of the present invention, the eccentricity limiting control system can, for example, be provided with a separate valve plunger which is directly actuated by the bimetal element. The plunger opens and closes the connection between the respective eccentricity limiting openings and the atmospheric pressure. Even if the bimetal element has a more or less linear temperature/way-characteristics, the use of a valve plunger actuated by the bimetal element allows for an individual defining and programming of a non-linear control of the maximum eccentricity limit dependent on the lubricant temperature T.

In an embodiment of the present invention, the valve plunger can, for example, be preloaded by a preload element into its closed position, wherein all eccentricity limiting openings are closed. This arrangement makes the eccentricity limiting control system fail-safe if the bimetal element should not work properly or break.

In an embodiment of the present invention, the switching temperatures TS of the eccentricity limiting control system can, for example, be between 0° C. and 100° C. The switching temperatures TS can, for example, be 0° C., 20° C. and/or 90° C.

The following is a detailed description of an embodiment of the present invention under reference to the drawings.

FIG. 1 shows a variable displacement lubricant pump 10 as a part of a pumping system 100 for supplying an internal combustion engine 70 with pressurized lubricant. From the internal combustion engine 70, the lubricant flows back via a flow-back conduit 86 to a lubricant tank 50 with more or less atmospheric pressure.

The pump 10 comprises a pump housing 11 having a cavity 16 in which a radially shiftable control ring 12 translates. The control ring 12 encircles a pump rotor 13 which is provided with numerous radially slidable vanes 14, whereby the vanes 14 rotate inside the control ring 12. The pump housing 11 comprises two pump side walls 15 of which one is not shown in FIG. 1 so that the inside of pump 10 can be shown. The pump side walls 15, the vanes 14, the pump rotor 13, and the control ring 12 define five rotating pump chambers 17. One of the pump side walls 15 is provided with a pump chamber inlet opening 18 and with a separate pump chamber outlet opening 19.

The control ring 12 is provided with a first plunger 24 housed in part in a first hydraulic control chamber 25, and with a second plunger 22 housed in part in a second hydraulic control chamber 23 opposite to the first hydraulic control chamber 25.

A pretensioned spring 28 inside the first control chamber 25 exerts a pushing force to the first plunger 24. Both hydraulic control chambers 25, 23 are formed inside and by the pump housing 11. The pump housing 11 also comprises a pump intake port 20 for sucking the lubricant from the lubricant tank 50, and a pump outlet port 21 for feeding lubricant with a discharge pressure to the internal combustion engine 70. A conduit 80 extends from the pump outlet port 21 to supply the internal combustion engine 70.

The lubricant, which is supplied to the internal combustion engine 70, is conducted to the second control chamber 23 via a pressure conduit 81, and the lubricant is fed to the first hydraulic control chamber 25 via pressure conduits 82, 87. More specifically, the lubricant in pressure conduit 82 is finally fed to the first hydraulic control chamber 25 via a pressure conduit 87 through a pressure throttle valve 67 in which a calibrated pressure drop occurs as the lubricant flows through.

The pressure conduits 82, 88 are connected to a control port 61 of a first pressure control valve 60. The first pressure control valve 60 comprises a cylinder 65 housing a piston 61. More specifically, the piston 61 comprises a first piston portion 62 and a second piston portion 64 connected to each other by a rod 63. The cross section of piston portions 62 and 64 are equal to the cross section of the cylinder 65, whereas the rod 63 is smaller in cross section than the cylinder 65. The cylinder 65 is provided with an inlet port 66 connected hydraulically to the first hydraulic control chamber 25 by a conduit 83, and is provided with an outlet port which is hydraulically connected to the lubricant tank 50 by a conduit 84. Pressure conduit 88 transfers the discharge pressure in pressure conduit 82 to the front surface of the first piston portion 62 of piston 61. The dashed line in FIG. 1 shows the situation when the inlet port 66 of the first pressure control valve 60 is closed by the second piston portion 64 of piston 61.

FIG. 2 shows a first embodiment of the eccentricity limiting control system 30 in more detail. The lateral control chamber wall 27 is provided with the first eccentricity limiting opening 26, the second eccentricity limiting opening 31, and the third eccentricity limiting opening 32. The three eccentricity limiting openings 26, 31, 32 are arranged with a radial distance to each other and do not overlap. The radial direction is the direction in which the first plunger 24 moves.

The eccentricity limiting control system 30 is provided with three independent bimetal elements 34, 35, 36 which define separate valve bodies connecting or disconnecting the eccentricity limiting openings 26, 31, 32 with the atmospheric pressure in the lubricant tank 50 via a lubricant channel 89. The bimetal elements 34, 35, 36 are bimetal strip bodies which are dished in two dimensions so that they have a sharp switching characteristic and relatively low hysteresis.

The switching temperature TS1 of the first bimetal element 34 is about 90° C., the switching temperature TS2 of the second bimetal element 35 is about 20° C., and the switching temperature TS3 of the third bimetal element 36 is about 0° C. As soon as the lubricant temperature T falls below the respective switching temperature TS, the respective bimetal element 34, 35, 36 switches into its open position as is shown in FIG. 2. The maximum eccentricity is therefore the lowest at a lubricant temperature T below 0° C.

FIG. 3 shows a second embodiment of an eccentricity limiting control system 30′ in more detail. In this embodiment, a single bimetal actuator element 42 is provided to directly shift a valve plunger 44 more or less linearly with the lubricant temperature T in a radial direction. The valve plunger 44 moves radially inside a valve cylinder 46. The valve plunger 44 is provided with a circular ring passage 45 which allows the lubricant to flow from one of the eccentricity limiting openings 26, 31, 32 through corresponding lubricant inlet openings 37, 38, 39 at the inner wall of the valve cylinder 46 to an outlet recess 49 of the valve cylinder if the circular ring passage 45 is aligned with one of the lubricant inlet openings 37, 38, 39. The form and the axial extension of the three lubricant inlet openings 37, 38, 39 can be different from each other to define different control characteristics. The lubricant outlet recess 49 is connected to the atmospheric pressure of the lubricant tank 50.

The valve plunger 44 is pretensioned by a preload element 48 into an axial closing position in which none of the eccentricity limiting openings 26, 31, 32 is connected to the lubricant tank 50. The preload element 48 can be realized as a coil spring.

FIG. 4 shows an alternative arrangement of eccentricity openings 26′, 31′, 32′, which are arranged to overlap with reference to the radial movement path of the control ring 12.

The present invention is not limited to embodiments described herein; reference should be had to the appended claims. 

What is claimed is: 1-7. (canceled)
 8. A variable displacement lubricant pump for providing a pressurized lubricant for an internal combustion engine, the variable displacement lubricant pump comprising: a control ring configured to be shiftable; a pump rotor comprising a plurality of slidable vanes which are configured to rotate in the control ring; a hydraulic pressure control comprising a control chamber which comprises a lateral control chamber wall, and a control ring plunger configured to be shiftable along the lateral control chamber wall, the hydraulic pressure control being configured to directly actuate and to control an eccentricity of the control ring; a first eccentricity limiting opening arranged in the lateral control chamber wall; a second eccentricity limiting opening arranged in the lateral control chamber wall; and an eccentricity limiting control system configured to connect or disconnect the first eccentricity limiting opening and the second eccentricity limiting opening to atmospheric pressure dependent on a lubricant temperature.
 9. The variable displacement lubricant pump as recited in claim 8, further comprising a third eccentricity limiting opening arranged in the lateral control chamber wall.
 10. The variable displacement lubricant pump as recited in claim 9, wherein the eccentricity limiting control system comprises at least one bimetal element configured to open or close at least one of the first eccentricity limiting opening, the second eccentricity limiting opening, and the third eccentricity limiting opening.
 11. The variable displacement lubricant pump as recited in claim 9, wherein, the first eccentricity limiting opening comprises a first bimetal element configured to close the first eccentricity limiting opening in a closed position of the first bimetal element, the second eccentricity limiting opening comprises a second bimetal element configured to close the second eccentricity limiting opening in a closed position of the second bimetal element, and the second eccentricity limiting opening comprises a third bimetal element configured to close the third eccentricity limiting opening in a closed position of the third bimetal element.
 12. The variable displacement lubricant pump as recited in claim 11, further comprising: a fourth bimetal element; and a separate valve plunger configured to open or close at least one of the first eccentricity limiting opening, the second eccentricity limiting opening, and the third eccentricity limiting opening depending on a position of the separate valve plunger, the separate valve plunger being actuated by the fourth bimetal element.
 13. The variable displacement lubricant pump as recited in claim 12, further comprising: a preload element; wherein, the separate valve plunger is preloaded by the preload element into a closed position where each of the first eccentricity limiting opening, the second eccentricity limiting opening, and the third eccentricity limiting opening is closed.
 14. The variable displacement lubricant pump as recited in claim 8, wherein a switching temperature TS of the eccentricity limiting control system is between 0° C. and 100° C. 